G'day Jack and wce
The Goodall mower patent looks like swing back blades and reads as having single bolted blades
but I have not seen images of the blades on a Goodall mower. (just to authenticate the patent)
The 1971 Fastcut ad was from New Guinea ,it's a little strange we could not find Australian
newspaper ads showing the Fastcut .
Jack, I was in no way inferring that someone was right and someone was wrong about anything in my post, please accept my apologies if it appeared that way.
Yep all good, as Jack said

The more facts we find helps to better understand vintage mowers.
A Herschel blade has the same basic shape as the Goodall blade .
Cheers
Max.